Surgical punches and graspers have been know in the art for some time. They generally involve a fixed or stationary member, an actuator extending from an actuator handle to the working end of the stationary member where the actuator engages a jaw member.
Actuation of the actuator causes the jaw member to pivot and open relative to the stationary member where tissue is inserted between the jaw member and die portion of the stationary member. The handle is then operated to close the jaw member relative to the stationary member where the engaged tissue is lacerated or grasped and can then be removed.
This type of operation is well known in the art and various types of surgical instruments have been developed. This process however puts large stresses on the components of the instruments due to the high forces needed to lacerate or grasp and remove some tissue. These high stresses cause premature failure of the instruments from wear or worse yet catastrophic failure of the components while in use, resulting in metal fragments or slivers being dispersed in the operative site. The metal fragments are often difficult to locate and remove causing unnecessary complications, increased medical time and greater possibility of less than optimum patient results. If metal fragments or slivers remain from catastrophic instrument failure and are not located and removed after the failure, a second procedure may be necessary to remove the metal fragments or slivers and to correct or rectify any tissue damage that may have occurred.
A typical failure mode in the prior art occurred when the pin attaching the jaw member to the stationary member or the pin attaching the actuator to the jaw member failed. Other failures occurred when the actuator bar was forced such that the bar bent, essentially locking the instrument. A jammed actuator bar would sometimes fail with the jaw member in a fully opened position and this would then cause damage to the operative site when removing the instrument with the jaw locked open. Another typical failure occurred when closing the jaw member on a piece of hard tissue, the actuator bar would fail and buckle upward immediately before the connection of the actuator bar and the jaw member. This was due to the necking down of the height and width of the actuator bar. Still other failures occurred when the contact surfaces between the actuator bar and the inner tip fractured and jammed the instrument.
Several other embodiments have addressed these problems by eliminating the pins typically used to attach the jaw member to the actuator and the jaw member to the stationary member. The pins have been replaced by a lug and groove arrangement. This procedure is costly and difficult to machine due to the precise dimensions required for smooth non-binding operation and the small size of the components.
Several other embodiments have utilized a pin for one of the attachments, either between the jaw member and actuator or between the jaw member and stationary member with a lug and groove for the other attachment. These prior art embodiments still had failures of the lug and groove surfaces due to high loading and small contact surfaces. These embodiments have tried to decrease the likelihood of catastrophic failure or premature failure by increasing the size of the components and attachments resulting in larger instrument size and more damage to the operative site from the increased size of the incisions and instruments. Large instrument size also decreases the finesse that can be obtained in the operation of the instruments in removing only specific tissue, resulting in removal of more tissue than may be necessary and therefore longer healing time and less than optimum patient results and recovery.
Consequently there is a need for an instrument in which the size can be kept at a minimum while the cutting force applied to the components can be kept high resulting in the minimizing of the likelihood of catastrophic failure or premature wear from overloading. The instrument should have a high strength to size ratio and have an optimum design to allow the highest operational forces for the smallest size with the appropriate materials.